The solubility of ibuprofen sodium dihydrate (ISD) in acetone + water mixtures was measured by the gravimetric method at temperatures ranging from (279.55 to 312.05) K. The measured solubilities were correlated by the modified Apelblat equation, the lambda h (Buchowski) equation, the vant Hoff model, the combined nearly ideal binary solvent/RedlichKister (CNIBS/R-K) equation, and the general single model. The modified Apelblat equation was the best model for correlating the solubility of ISD, while the general single model fits the best for mixed solvents. The standard enthalpy, entropy, and Gibbs energy of the dissociation process of ISD were calculated by the vant Hoff equation and the modified Apelblat model. In addition, there was a maximum value of solubility at a certain acetone mole fraction in the acetone + water mixture.